Whether you’re on your first pair of glasses or your tenth, you may still be put off by phrases like “temple arms” and “lens height,” especially if you’re interested in shopping for your own frames. This visual guide shows you what all those terms mean so you can buy confidently.

This is another graphic from the folks at Zenni Optical (one of your favorite online glasses stores, and again, someone with a vested interest in having you buy your frames from them, so keep that in mind) but the information within is good to know. Using a pair of glasses as a guide, they diagram out lens height and width, frame width, temple arms, and more, so you understand what you’re looking at when a frame retailer—online or off—explains the measurements for their frames. They even offer a few tips to keep your lenses thinner and frames more comfortable. Check out the whole graphic below.